PLL Out-of-Lock Condition

If the frequency difference between the reference clock

input and the VCO at the PFD input becomes within

500ppm, the PLL is considered to be in lock (LOCK =

0). When the frequency difference between the refer-

ence clock input and the VCO at the PFD input

becomes greater than 800ppm, the PLL is considered

out-of-lock. It should be noted that the LOCK indicator

is not part of the frequency qualification used for the

INxFAIL indicators.

Input and Output Frequencies

The MAX3671 input and output dividers are configured

using four-level control inputs DM, DA, and DB. Each

divider is independent and can have a unique setting.

The input connection and associated frequencies are

listed in Tables 1, 2, and 3.

Output-Enable Controls

Each output group (A and B) has a three-level control

input OUTA_EN and OUTB_EN. See Tables 4 and 5 for

configuration settings. When clock outputs are dis-

abled, they are high impedance. Unused enabled out-

puts should be left open.

Power-On-Reset (POR)

At power-on, an internal signal is generated to hold the

MAX3671 in a reset state. This internal reset time is

the POR time, the outputs are held to logic-low (OUTxx

= low and OUTxx = high). See Table 6 for output signal

status during POR. After this internal reset time, the PLL

starts to lock to the reference clock selected by

SEL_CLK.

Low-Jitter Frequency Synthesizer

with Selectable Input Reference

______________________________________________________________________________________

11

Table 1. Divider M Configuration for Input

Frequencies

CONNECTION FROM DM PIN

INPUT FREQUENCY (MHz)

GND

62.5

125

Open

250

10k

to GND

312.5

Table 2. Divider A Configuration for

A-Group Output Frequencies

CONNECTION FROM DA PIN

OUTPUT FREQUENCY AT

OUTA[3:0] (MHz)

GND

62.5

125

Open

156.25

10k

to GND

312.5

Table 3. Divider B Configuration for

B-Group Output Frequencies

CONNECTION FROM DB PIN

OUTPUT FREQUENCY AT

OUTB[4:0] (MHz)

GND

62.5

125

Open

250

10k

to GND

312.5

Table 4. OUTA[3:0] Enable Control

CONNECTION FROM

OUTA_EN PIN

A-GROUP OUTPUT ENABLED

A-GROUP OUTPUT DISABLED TO HIGH

IMPEDANCE

GND

OUTA0, OUTA1, OUTA2, OUTA3

—

—

OUTA0, OUTA1, OUTA2, OUTA3

Open

OUTA0, OUTA1

OUTA2, OUTA3

Table 5. OUTB[4:0] Enable Control

CONNECTION FROM

OUTB_EN PIN

B-GROUP OUTPUT ENABLED

B-GROUP OUTPUT DISABLED TO HIGH

IMPEDANCE

GND

OUTB0, OUTB1, OUTB2, OUTB3, OUTB4

—

OUTB0

OUTB1, OUTB2, OUTB3, OUTB4

Open

OUTB0, OUTB1, OUTB2

OUTB3, OUTB4

mode of operation.

mode of operation.